Mutations in genes affecting pain transmission start to be known, the investigators are investigating a mutation in a glycine channel, which has an influence on pain modulation. Pain modulation is the ability of the central nervous system to enhance or diminish the sensation of pain. The investigators therefore will test patients and healthy volunteers with quantitative sensory tests, basically determining the point at which a stimulation just starts to induce pain. These tests are reliable and permit a direct comparison between healthy volunteers and patients with the affected glycine gene.

Further study details as provided by University Hospital Inselspital, Berne:

Primary Outcome Measures:

Pressure pain detection threshold measured in kPA, measured with electronic pressure algometer applied at the centre of the pulp of the 2nd toe [ Time Frame: Within 0 to 33 seconds after the beginning of the stimulation ] [ Designated as safety issue: No ]

Pain detection thresholds will be measured with an electronic pressure algometer applied at the center of the pulp of the 2nd toe. The probe has a surface area of 1 cm2. The pressure is increased from 0 at a rate of 30kPa/s to a maximum pressure of 1000kPa. Pain detection threshold is defined as the point at which the pressure sensation turns to pain. The subjects are instructed to press a button when these points are reached. The algometer displays the pressure intensity at which the button is pressed.

Secondary Outcome Measures:

Electric pain reflex, as measured with electromyography from the biceps femoris and the rectus femoris muscles [ Time Frame: Within 50 to 150 ms after the beginning of stimulation ] [ Designated as safety issue: No ]

Electromyographic (EMG) reflex responses to electrical stimulation will be recorded from the middle of the biceps femoris and the rectus femoris muscles (Ag/AgCl-electrodes). A 25 ms, train-of-five, 1 ms, square-wave impulse (perceived as a single stimulus), will be delivered. The current intensity will be increased from 1 mA in steps of 1 mA until: 1) a biceps femoris reflex with an amplitude exceeding 20 mV for at least 10 ms in the 50-150 ms post-stimulation interval will be detected (single stimulus reflex threshold); and 2) a pain sensation will be evoked (single stimulus pain threshold).

Heat and cold pain detection thresholds, as measured with a thermode in degrees Celsius [ Time Frame: Within 0 to 14 seconds after the beginning of the stimulation ] [ Designated as safety issue: No ]

A thermode will be applied to the skin. The temperature of the thermode will be continuously increased from 30 ºC to a maximum of 50.5 ºC at a rate of 1.5 ºC/s. Pain detection threshold is defined as for pressure stimulation. The subjects are instructed to press a button when this point is reached. For cold stimulation, the temperature of the thermode will be continuously decreased from 30 ºC to a minimum of 0 ºC at a rate of 1.5 ºC/sec. Pain detection threshold is defined as for pressure stimulation. The subjects are instructed to press a button when this point is reached.

Ice water pain threshold of the hand as measured in seconds the hand was left in the water, measured with ice water container [ Time Frame: Within 0 to 2 minutes after the beginning of the stimulation ] [ Designated as safety issue: No ]

The device consists of a container separated into an outer and an inner part by a mesh screen. The mesh screen prevents direct contact between the ice (placed in the outer part) and the hand of the subject (placed in the inner part). The water is regularly mixed to maintain the temperature in the inner part near to 0°C. The subject places his hand, wide open and to the wrist, into the inner part of the container. He is asked to keep it in the water until he feels an intolerable sensation of pain and is forced to remove his hand from the container, in any case for a maximum time of 2 min.

Pressure pain detection threshold measured in kPA, measured with electronic pressure algometer applied at the centre of the pulp of the 2nd toe [ Time Frame: At the end of the experiment, expected to be after 30 minutes on average ] [ Designated as safety issue: No ]

Pain detection thresholds will be measured with an electronic pressure algometer applied at the center of the pulp of the 2nd toe. The probe has a surface area of 1 cm2. The pressure is increased from 0 at a rate of 30kPa/s to a maximum pressure of 1000kPa. Pain detection threshold is defined as the point at which the pressure sensation turns to pain. The subjects are instructed to press a button when these points are reached. The algometer displays the pressure intensity at which the button is pressed.

In the setting of comparing patients with a genetic mutation and healthy volunteers blinding of the PI would demand a substantial increase in co-workers (i.e. recruitment, selection of age-and sex matched volunteers), reason why no blinding was chosen.

Affected patients will be compared to age and sex matched volunteers, recruited after completion of testing 23 hyperekplexia patients.

Other: No intervention

The testing will be the same for healthy volunteers and patients with a mutations in the glycine channel.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01476514